1. Field of the Invention
This invention relates to an image read-out and reproducing method for carrying out read out of an image stored on an image storage sheet such as a stimulable phosphor sheet and reproduction of the image thus read out on a recording sheet by use of a single scanning system, and an apparatus for carrying out the method. This invention particularly relates to an image read-out and reproducing method wherein semiconductor lasers are utilized as a scanning light source, and an apparatus for carrying out the method. This invention also relates to a multi-semiconductor-laser light source device for use in the apparatus.
2. Description of the Prior Art
Image read-out apparatuses for reading out an image recorded on a sheet by two-dimensionally scanning a light beam such as a laser beam on the sheet carrying the image recorded thereon, and by detecting light carrying the image information (for example, light reflected by the sheet, light transmitted therethrough, or light emitted thereby), which light is obtained when the sheet is exposed to the light beam, by use of a photo detecting means provided with a photomultiplier or the like have heretofore been widely used as scanners for plate making, in computer input devices, and in facsimile image read-out devices.
On the other hand, when certain kinds of phosphors are exposed to radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the amount of energy stored during exposure to the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor. As disclosed in U.S. Pat. Nos. 4,258,264, 4,276,473, 4,315,318 and 4,387,428 and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet) is first exposed to radiation which has passed through an object such as the human body in order to store a radiation image of the object thereon, and is then scanned with stimulating rays such as a laser beam which cause it to emit light in proportion to the amount of energy stored during exposure to the radiation. The light emitted by the stimulable phosphor sheet upon stimulation thereof is photoelectrically detected and converted into an electric image signal, and the image signal is used to reproduce the radiation image of the object as a visible image on a recording material such as a photographic film, a display device such as a cathode ray tube (CRT), or the like.
In the aforesaid radiation image recording and reproducing system, the radiation image stored on the stimulable phosphor sheet is read out by deflecting stimulating rays and causing them to scan the stimulable phosphor sheet in a main scanning direction in a radiation image read-out apparatus, simultaneously moving the stimulable phosphor sheet with respect to the stimulating rays in a sub-scanning direction approximately normal to the main scanning direction, thereby scanning the overall surface of the stimulable phosphor sheet with the stimulating rays, and photoelectrically detecting the light emitted by the scanned portion of the stimulable phosphor sheet by use of a photodetector.
On the other hand, the image which has been read out by a read-out apparatus such as the aforesaid radiation image read-out apparatus is reproduced as a visible image by, for example, causing a light beam modulated in accordance with the image signal obtained by the read-out apparatus to scan a recording sheet in the main scanning direction while the recording sheet is being moved with respect to the light beam in the sub-scanning direction, and thus recording the visible image on the recording sheet. Therefore, in order to form the final visible image of the image, which was stored on an image storage sheet such as a stimulable phosphor sheet, on a recording sheet, it has heretofore been necessary to provide the read-out apparatus for reading out the image from the image storage sheet and the reproducing apparatus for reproducing the image on the recording sheet.
In recent years, various attempts have been made to simplify the overall radiation image recording and reproducing system as much as possible, to make the apparatus smaller as a whole and to reduce the manufacturing cost thereof. As one of such attempts, a novel read-out and reproducing apparatus has been proposed in Japanese Unexamined Patent Publication No. 58(1983)-184677. In the proposed read-out and reproducing apparatus, the conventional read-out apparatus, wherein scanning with a light beam is carried out, and the conventional reproducing apparatus, wherein scanning with a light beam is carried out, are combined with each other so that both image read out and image reproduction may be carried out by use of a single scanning system.
However, in the read-out and reproducing apparatus mentioned above, scanning must be carried out by use of a light beam of a predetermined intensity in the course of image read-out, and scanning must be carried out by use of a light beam modulated in accordance with the image information in the course of image reproduction. Therefore, in the read-out and reproducing apparatus proposed in Japanese Unexamined Patent Publication No. 58(1983)-184677, a light modulator is moved into the path of the light beam in the course of image reproduction, and is retracted from the path of the light beam in the course of image read-out. Therefore, a mechanism for moving the light modulator is necessary, and the configuration of the apparatus becomes complicated. Accordingly, the applicant has proposed in Japanese Patent Application No. 62(1987)-335505corresponding to U.S. Ser. No. 195,333 a read-out and reproducing apparatus wherein a light modulator such as an acousto-optic modulator (AOM) is secured in an optical path of the light beam so that the mechanism is simplified and a suitable light beam is obtained both in the course of image read out and in the course of image reproduction.
It has heretofore been known to utilize a semiconductor laser as a means for producing read-out light for image read out or reproducing light for image reproduction. The semiconductor laser has advantages over a gas laser in that the semiconductor laser is small, cheap and consumes little power. Also, with the semiconductor laser, direct analog modulation can be achieved by controlling the drive current. Therefore, when both image read out and reproduction are to be carried out with a single scanning system, a light modulator such as an AOM need not be provided or moved into and out of an optical path.
However, the output power of the semiconductor laser is low (20 mW to 30 mW) when radiation is carried out continuously. Therefore, the semiconductor laser is not suitable for use as a means for producing read-out light in cases where, for example, a high energy light beam is required to stimulate a phosphor sheet in order to read out a image stored thereon.
In order to obtain a scanning laser beam having a sufficiently high energy from a semiconductor laser having a low power output, a plurality of semiconductor lasers may be used, and laser beams radiated out of the semiconductor lasers may be combined so as to multiply the power of the individual lasers.
In general, in order to combine the laser beams produced by a plurality of semiconductor lasers and to use the combined laser beams as scanning light, the laser beams produced by the semiconductor lasers are collimated respectively by collimator lenses, guided along optical paths parallel and close to one another, and made to impinge upon a light deflector.
However, in the aforesaid read-out and reproducing apparatus wherein both image read out and reproduction are carried out by use of a single scanning system, the scanning light used during image reproduction need not have as high an intensity as the scanning light used during image read out. Therefore, in cases where a light source device comprising a plurality of semiconductor lasers is used as a light source for producing read-out light, a light source for producing reproducing light having a comparatively low intensity must be provided additionally. As a result, the configuration of the read-out and reproducing apparatus becomes complicated, and the apparatus becomes large.